Photographic films and their preparation



United States Patent O PHOTOGRAPHIC FILMS AND THEIR PREPARATION Francis Peter Alles, Westficld, and William Russell Saner, Plainfield, N. J., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application May 27, 1952, Serial No. 290,332

11 Claims- (Cl. 95-9) This invention relates to photographic film elements. More particularly it relates to transparent photographic film elements which have a polyvinyl acetal color formersilver halide dispersion anchored to the support by means of a substratum composed of a copolymer of vinylidene chloride, an acrylic ester and itaconic acid. Still more particularly it relates to such elements wherein the film base is composed of an oriented highly polymeric linear ester of a dicarboxylic acid and a dihydric alcohol. The invention also relates to a method of preparing such elements.

An object of this invention is to provide photographic film elements wherein a polyvinyl acetal color formersilver halide dispersion is firmly anchored to a film base.

Another object is to provide such elements which have improved dimensional stability. 'A further object is to provide such elements wherein the film base is composed of an oriented highly polymeric ester of a dicarboxylic acid and a dihydric alcohol. Still other objects will be apparent from the following description of the invention.

The use of polyvinyl acetal color formers, which are hydrophilic to water-soluble in character, as the binding agent for silver halide grains has been disclosed in a number of patents in the past six years. It has been difficult, however, to obtain adequate anchorage between thin layers composed of such dispersions and the usual types of hydrophobic film base. This is particularly true of film base composed of highly polymeric esters of dicarboxylic acids and dihydric alcohols and especially films composed of polyethylene terephthalates. These polyvinyl acetal dispersions do not have good adherence to the conventional gelatin sublayers which have been used for many years in anchoring colloid silver halide emulsion layers to hydrophobic films.

It has been found that if a hydrophobic film base is coated with a thin layer of a copolymer of vinylidene chloride, an acrylic ester and itaconic acid that this layer has excellent adherence to the film base and can be made to adhere tenaciously to a layer of polyvinyl acetal color former-silver halide dispersion in two ways, (1) by heating the coated film element to a temperature of at least 70 C. after the polyvinyl acetal silver halide dispersion layer has been applied, or (2) by first applying to the layer of copolymer a'thin layer of a hydroxyl polymer which contains a plurality of recurring intralinear groups as polymer-forming units, said polymers being water-soluble to hydrophilic in character. The adherence of the latter intermediate substratum can also be improved by heatingthe coated film base to a temperature of at least 70 C. before applying the silver halide dispersion. This heating step, however, can be applied after thepolyvinyl acetal color-.former-silver halide dispersion has been coated onto the layer of hydroxyl polymer.

Synthetic hydroxyl polymers of the water-soluble and hydrophilictype include polyvinyl alcohol and its partially substituted water-soluble lower fatty acidesters, lower alkyl esters, and lower acetals. Polyvinyl alcohol is a tough, white, amorphous material. water. The more highly polymerized varieties are soluble in hot water and the medium or lower polymers aresol uble in cold water. They are usuallyprepared by hydrolysis of polyvinyl esters, such as polyvinyl acetate,

2,698,240 Patented Dec. 28, 1954 partly hydrolyzed esters which contain a large number of recurring vinyl alcohol units I (-CH2CHOH) copolymers with various mono-ethylenically unsaturated compounds having a terminal CH2=C group, such as It is soluble in vinyl chloride, acrylic acid esters, e. g., methyl acrylate; methacrylic acid esters, e. g., methyl methacrylate; and mono-olefins, e. g., ethylene. The completely hydrolyzed ethylene/vinyl acetate interpolymerswhich are described in McQueen 2,397,866 and Roland 2,386,347 form an important class of synthetic hydroxyl polymers useful as binding agents for the silver halide emulsions made in accordance with this invention.

The solutions used to coat the substratum of the synthetic hydroxyl polymer, free from color former nuclei, may contain a coagulating agent, e. g., boric acid or a boric acid ester of a polyhydric alcohol, e. g., an ester prepared by reacting an alcohol. such as ethylene glycol, diethylene glycol, triethylene glycol, erythritol, sorbitol, mannitol, etc., with boric acid or a mixture of boric acid and borax, by heating the admixture to C. to C'. A copious evolution of Water occurs. The resulting products are viscous syrups or resins of a colloidal nature and have a high molecular weight and complex structure. They are readily soluble in Water but are substantially insoluble in hydrocarbons but probably hydrolyze to the boric acid and glycol in water. Their preparation is described in United States Patents 1,953,741, 2,223,349, 2,223,948, 2,223,949, and 2,224,011. These compounds have been referred to as boriborates:

In carrying out the invention a hydrophobic film which may be composed of a cellulose carboxylic acid ester, e. g., cellulose acetate, cellulose acetate proprionate, cellulose acetate butyrate, cellulose nitrate, cellulose propionate; a superpolymer, e. g., a superpolyamide (nylon), an orientable highly polymeric linear ester of a dicarboxylic acid and a dihydric alcohol, e. g., polyethylene terephthalate, polyvinyl chloride, etc., is coated with a copolymer of vinylidene chloride, an acrylic ester and itaconic acid either from an organic solvent solution or from an aqueous dispersion. When an organic solvent solution is used the solvent should have only a mild solvent actiononthe base so that it will not appreciably dissolve the film base but have a superficial effect and merely soften or bite into the surface of the base. The substrata, composed of a vinyl alcohol polymer and/or the polyvinyl acetal color former-silver halide dispersion coatings are formed by coating them onto the layer of vinylidene chloride copolymer.

In order that the three component copolymers described above will adhere to the base tenaciously and have the requisite degree of flexibility, it is essential that the initial relative proportions of monomers in the reaction mixture be within the following ranges:

The useful ethylenically unsaturated esters which may be used in the copolymers are the alkyl esters of acrylic and methacrylic acids having from 1 to 18 carbon atoms in the alkyl group- (e. g., methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, n-dodecyl methacrylate, n-octadecyl methacrylate, methyl acrylate,

of concentration of 0.1% to 1.0%.. improved solubility and viscosity valuesare-obtainedv byconductiugdhe polymerization in the. presence. of. mercaptans. such; as; ethyl mercaptan, lauryl 'mercaptan, tertiary dod'ecyl'mercaptan, etc., whichare effective, in reducingicrosswlifnking. inthe copolymer. In general, themercaptanmshould beused inconcentrations of 0.l,%..to 5.0%.by, weight, based on the, weight of polymerizable monomerspresent. in the charge.

The .copolymers of this invention .canbe :coated ,on ,the hydrophobic film base or support b,y any suitabletechs nique, e. g., coating from ahopper, skiml coating where the surface .of the film passes under arollerandcontacts with the surface of the liquid coatingnwith applicator or transfer rolls, spray coating, etc. Doctor blades, air doctor blades, etc., can be used to remove excess liquid.

The invention will be further illustrated but isnot intended to be limited by the following examples.

Example I A sample of polyethylene terephthalate filmbasehaving a thicknessof 0.003 inch, melting pointof above 200 C. and an intrinsic viscosity of 0.50 in a mixture of 2,4,6-trichlorophenol and phenol (70:100' parts by weight) was coated with an aqueous dispersion of the vinylidene chloride-methyl acrylate-itaconic acid copolymer described in Alles & SanerU. S. patent'application Ser. No. 151,274, filed March 22, 1950, now PatentNo. 2,627,088. After drying at 50 C., and heating for two minutes at 100 C., the film was coated with a polyvinyl acetal color-former-silver halide dispersion, containing approximately 1.77% by weight of. silver iodobromide, composed of approximately 0.9% silver iodide and 99.1% silver bromide, dispersed in the polymeric colorformer (4.12% by weight of the total dispersion.) described in U. S. Patent 2,513,190. After drying, the silver halide dispersion was found to have good adherence to the film base. The film was exposed and processed as follows:

(1) Developed for minutes-a t--68 F. in a solution having the following composition:

Grams Para-aminodiethylaniline hydrochloride 2.5 Sodium sulfite 10.0 Sodium carbonate 46.8 Potassium bromide- 2.0

Water to make 1 liter (2) Given a 30second rinse in water, (3) Treated for 5 minutes at 68 F. in the. following fixing bath:

Sodium thiosulfate v grams 240.0 Sodium sulfite d0 :0 Sodium tetraborate do- 18.0 Glacial acetic acid cc' 12.0 Potassium aluminum sulfate "grams-.. 20.0

Water to make 3-liters (4) Given a 5 minute rinse in water, (5) Treated for 5 minutes at 68 F. in the following bleaching bath:

Grams Potassium ferricyanide -,u 100.0 Boric acid 10.0 Sodium tetraborate 5.0

The wet and dry anchorage, after processing, were found to be'satisfactory'.

Example II A second color film with a polyethylene terephthalate base of the kind described in Example I was treated as in said example except that the film was stretched biaxially after the vinylidene chloride-methyl.acrylate-itaconic acid copolymer layer had been applied and before the color former emulsion was applied. The resulting film was exposed and processed-as, described in Example I with similar results.

Examplelll A sample of a polyethylene terephthalate film base of the type used in Example .I was treatedwith a copolymer of vinylidene chloride-methyl acrylate-itaconic acid of the type used in Example I, then stretched biaxlally and coated with a solution of.the.following composition:

Percent Meta (benzoylacetamido)benzaldehyde sodiumo-sulfobenzaldehyde-polyvinyl mixediacetal 5 Water 79 M hano After dryingatz507 C.,.the,film was further treated with a solutionofthe following composition:

Percent Meta (benzoylacetamido)benzaldehyde sodiumo-sulfobenzaldehyde-polyvinyl mixed acetal Boric acid 1.:1 Diisopropanolamine 1.3 Acetone 40.0 Ethyl alcohol 72f) .5533

After dryingatSO C., the ,film was heatedlat C. for 2 minutes and coated with a color-former dispersion of the type describedin Example I. The adhesion, both wetrand 'dry, after exposing' the'film -and processing in the usual manner, was.good. The above polyvinyl acetal is described in Example. I'of Martin 2,513,189.

Example] V After-drying at-50 C., the film washeatedat C.

: for- 5 minutes and was further treated with a solution of the following composition:

Percent Boric acid; 1.9 Diisopropanolamine 1.3 Water 96.8

Afterdryingrat 50 C.; the .filrn was :coated ,withrapolyvinyl-acetal tcolor-former silver halide. emulsion, containing 1.77% by weight:of:silver iodobromide, composed of approximately 0.9% silver iodide and 99.1% silver bromide, dispersed in .thepolymeric color former (4.12% by weight of the total emulsion) described in Martin U. S. Patent No. 2,513,190. After. drying, theemulsion wasfound-to have. goodfadherence. to. the film, base. lt wasexposed andprocessedas described in Example 1. Wet and .dry. anchorage, after processing, werev good.

Example" V" A sample of apolyethyleneterephthalatefilm base of the'type used in Example], was coated on'both-sides with a copolymer of vinylidene chloride of the :type used in Example I, stretchedbiaxially, and: was coated on one 'sidewith the twosubbing solutions asset forth in Example III. After drying," the film waszsubjectedto a temperatureof 100 C. for'severalminutes'and was then-coated-with the following-dispersionsand solutions, in the order listed.

(1) Apolyvinyl acetal color-former-silver halide dis.- persion containing 1.7 7 byweight of silver-iodobromide; composed of approximately 0.9% silver 'i0dld-aIldi99.'1%

silver bromide, dispersed in the polymeric color former (4.12% by weight of the total dispersion) described in U. 5. Patent No. 2,513,190.

(2) A 1.15% solution of polyvinyl alcohol (99% hydroiyzed polyvinyl acetate, a 4% solution of which, in

water, had a viscosity of D5 centipoises at C.) in a mixture of water and alcohol.

(3 A polyvinyl acetal color-former-silver halide dispersion containing approximately 2.2% silver bromide dispersed in the polymeric color rormer (2.8% by weight of the total dispersion) described in U. S. Patent 2,489,655.

(4) 'lhe same solution given under (2).

(5) A polyvinyl acetal color-former-silver halide dispersion containing approximately 1.15% silver bromide dispersed in the polymeric color former (4.15% by weight of the total dispersion) described in U. S. Patent 2,476,988. This dispersion also contained dissolved ghefiain, the yellow dye Tartrazine (Colour Index No.

After drying, this composite light-sensitive element was found to adhere well to the film base. The film was exposed and processed as described in Example I. The wet and dry anchorage were found to be satisfactory.

While a heating temperature of at least 70 C. has been referred to above the examples include higher temperatures and indeed temperatures up to 150 C. or more can be used if they do not deleteriously affect the coated layers. This can be determined visually with respect to the particular color former. When a gelling hydroxyl polymer sublayer or non-gelling hydroxyl polymer sublayer is used the heating step may precede the application of the polyvinyl acetal color former layer.

'lhe invention is, of course, not limited to the foregoing examples as any of the film bases referred to above may be substituted, in some cases without stretching, with similar results.

Similarly, the invention is not limited to the use of the specific polyvinyl acetal color formers given in the examples as many other hydrophilic to water-soluble acetals of this general type can be substituted with similar results. Among such additional suitable polyvinyl acetal color formers are those described in the following U. S. Patents: Jennings 2,397,864, Woodward 2,423,572, Mc- Queen 2,464,597, Corner & Woodward 2,465,067, Martin 2,472,910, Martin 2,538,257, Martin 2,476,988, Mc- Queen 2,477,462, Martin 2,489,655, McQueen 2,513,190, and Martin 2,518,704.

It is to be understood that in the case of color films for multicolor photography they will contain several superposed polyvinyl acetal color-former-silver halide emulsion layers which are so arranged and sensitized that they record different colors of the visible spectrum. These color formers can be selected to yield yellow, blue-green (cyan), and magenta, etc., quinoneimine, aszomethine,

etc., dyes in the appropriate layers as is common in the art and described in Jennings 2,497,864 and other patents described above. Filter dyes may be present in one or more of the above color former layers or in a separate stratum, e. g., a polyvinyl alcohol or equivalent hydroxyl polymer layer as described above. In general, a yellow filter dye is used in a stratum above the two light-sensitive layers most distant from the camera side of the film.

An advantage of the invention is that it provides a simple and effective process for improving the anchorage between a polyvinyl acetal color former layer and a hydrophobic film base. Another advantage is that the process can be carried out with conventional equipment. Still other advantages will be apparent from the above.

This invention is a continuation-in-part of U. S. application Ser. No. 151,274, filed March 22, 1950.

As many widely different embodiments of this invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited except as defined by the claims.

What is claimed is:

1. The process which comprises coating a waterperrneable hydroxyl polymer layer onto a stratum composed of a tri-component coploymer made from to 96% of vinylidene chloride, 3.5 to 64.5% of an ethylenically unsaturated ester and 0.5 to 25% of itaconic acid monomers, all percentages being by weight, said ester being taken from the group consisting of alkyl esters of acrylic and methacrylic acids having 1 to 18 carbon atoms in the alkyl group, acryonitrile, methacrylonitrile and vinyl chloride: said stratum being on a hydrophobic 6 film base, and heating the coated layer to a temperature from 70 C. to 150 C.

2. A process as set forth in claim 1 wherein said hydroxyl polymer is a polyvinyl acetal color-former.

3. A process as set forth in claim 2 wherein said acetal has light-sensitive silver salts uniformly dispersed therethrough.

4. 'lhe process which comprises coating a Waterpermeable hydroxyl polymer layer onto a stratum composed of a tri-component copolymer made from 35m 96% of vinylidene chloride, 3.5 to 64.5 of an ethylenically unsaturated ester and 0.5 to 25% of itaconic acid monomers, all percentages being by weight, said ester being taken from the group consisting of alkyl esters of acrylic and methacrylic acids having 1 to 18 carbon atoms in the alkyl group, acrylonitrile, methacrylo nitrile and vinyl chloride; said stratum being on an oriented highly polymeric ester of a polymethylene glycol of 2 to 10 carbon atoms and terephthalic acid, said ester having a melting point from 200 C. to 300 C., and heating the coated base to a temperature from 70 C. to 130 C.

5. A process as set forth in claim 4 wherein said bydroxyl polymer is a polyvinyl acetal color-former.

6. A process as set forth in claim 5 wherein said acetal has light-sensitive silver halides uniformly dispersed therethrough.

7. The process which comprises coating a light-insensitive, water-permeable hydroxyl polymer layer onto a stratum composed of a tri-component copolymer made from 35 to 96% of vinylidene chloride, 3.5 to 64.5% of an ethylenically unsaturated ester and 0.5 to 25% of itaconic acid monomers, all percentages being by weight, said ester being taken from the group consisting of alkyl esters of acrylic and methacrylic acids having 1 to 18 carbon atoms in the alkyl group, acrylonitrile, methacrylonitrile and vinyl chloride; said stratum being on an oriented highly polymeric ester of a polymethylene glycol of 2 to 10 carbon atoms and terephthalic acid, said ester having a melting point from 200 C. to 300 C., heating the coated base to a temperature from 70 C. to 130 C., coating an aqueous dispersion of light-sensitive silver halides in a polyvinyl acetal color-former onto said polymer layer and drying the resulting film element.

8. The process which comprises coating a light-insensitive, water-permeable hydroxyl polymer layer onto a stratum composed of a tri-component copolymer made from 35 to 96% of vinylidene chloride, 3.5 to 64.5% of an ethylenically unsaturated ester and 0.5 to 25% of itaconic acid monomers, all percentages being by weight, said ester being taken from the group consisting of alkyl esters of acrylic and methacrylic acids having 1 to 18 carbon atoms in the alkyl group, acrylonitrile, methacrylonitrile and vinyl chloride; said stratum being on an oriented highly polymeric ester of a polymethylene glycol of 2 to 10 carbon atoms and terephthalic acid, said ester having a melting point from 200 C. to 300 C., coating an aqueous dispersion of light-sensitive silver halides in a polyvinyl acetal color-former onto said polymer layer and drying the resulting film element, heating the coated base to a temperature from 70 C. to C.

9. A photographic element comprising a film base composed of an oriented highly polymeric ester of a polymethylene glycol of 2 to 10 carbon atoms and terephthalic acid, said ester having a melting point from 200 C. to 300 (3., bearing in order a substratum composed of a tri-component copolymer made from 35 to 96% of vinylidene chloride, 3.5 to 64.5 of an ethylenically unsaturated ester and 0.5 to 25 of itaconic acid monomers, all percentages being by weight, said ester being taken from the group consisting of alkyl esters of acrylic and methacrylic acids having 1 to 18 carbon atoms in the alkyl group, acrylonitrile, methacrylonitrile and vinyl chloride: said stratum being a layer of a water-soluble to hydrophilic hydroxyl polymer containing a plurality of intralinear --CHzCHOH-- groups as polymer units and at least one layer of lightsensitive silver halides dispersed in a polyvinyl acetal color-former.

10. A photographic element comprising a film base composed of an oriented highly polymeric ester of a polymethylene glycol of 2 to 10 carbon atoms and terephthalic acid, said ester having a melting point from 200 C. to 300 C., bearing in order a substratum comgposed alof av Kiri-701111301160! --.eopolyn'ler macle from} 351.10

96% of vinylidene chloride, ;3'.5"-:to r64';$% 20f :.ethylenically unsaturated ester:and-'0.5l=to;25%:of.itaconic acid monomers, :allwpercentages :being by .weight,.=s aid :ester being takenCfrorn;;theugroupeconsistingzof alkyl esters ..of v.acrylic .:.and :.methacry1ic'--acids %having .1 to 18 carbon atoms in the alkyl group, acrylonitrile, -meth acrylonitrilexand vinyl chloride: said..stratum being a 1 layer of polyvinyl ;alcohol andqat least one layer of-light- .-sensitive silver ,halides dispersed. in :arpolyvinyl zacetal color-former having -av plurality :of -YCH2..C'HOH groups was-polymer units.

intralinear Number Name Date 398,039 DIAlelio Oct. 6, 1942 ..2;491,023 Alles etaal. .Dec. 13, 1949 :10 2 534,326 Weaver Dec. 19, 1950 :.2;'6 0 6,835 Jennings Aug. 12, 1952 2,627,088 Alles-set'al.v ...Feb.'31 195 

1. THE PROCESS WHICH COMPRISES COATING A WATERPERMEABLE HYDROXYL POLYMER LAYER ONTO A STRATUM COMPOSED OF A TRI-COMPONENT COPLOYMER MADE FROM 35 TO 96% OF VINYLIDENE CHLORIDE 3.5 TO 64.5% OF AN ETHYLENICALLY UNSATURATED ESTER AND 0.5 TO 25% OF ITACONIC ACID MONOMERS, ALL PERCENTAGES BEING BY WEIGHT, SAID ESTER BEING TAKEN FROM THE GROUP CONSISTING OF ALKYL ESTERS OF ACRYLIC AND METHACRYLIC ACIDS HAVING 1 TO 18 CARBON ATOMS IN THE ALKYL GROUP, ACRYONITRILE, METHACRYLONITRILE AND VINYL CHLORIDE: SAID STRATUM BEING ON A HYDROPHOBIC FILM BASE, AND HEATING THE COATED LAYER TO A TEMPERATURE FROM 70* C. TO 150* C. 